gc: align structs according to max alignment of fields
cc: same
runtime: test cc alignment (required moving #define of offsetof to runtime.h)
fix bug260
Fixes #482.
Fixes #609.
R=ken2, r
CC=golang-dev
https://golang.org/cl/3563042
diff --git a/src/cmd/5c/swt.c b/src/cmd/5c/swt.c
index 7740ad2..43eb73c 100644
--- a/src/cmd/5c/swt.c
+++ b/src/cmd/5c/swt.c
@@ -606,7 +606,7 @@
}
int32
-align(int32 i, Type *t, int op)
+align(int32 i, Type *t, int op, int32 *maxalign)
{
int32 o;
Type *v;
@@ -620,7 +620,9 @@
break;
case Asu2: /* padding at end of a struct */
- w = SZ_LONG;
+ w = *maxalign;
+ if(w < 1)
+ w = 1;
if(packflg)
w = packflg;
break;
@@ -628,10 +630,16 @@
case Ael1: /* initial align of struct element */
for(v=t; v->etype==TARRAY; v=v->link)
;
- w = ewidth[v->etype];
- if(w <= 0 || w >= SZ_LONG)
- w = SZ_LONG;
- if(packflg)
+ if(v->etype == TSTRUCT || v->etype == TUNION)
+ w = v->align;
+ else {
+ w = ewidth[v->etype];
+ if(w == 8)
+ w = 4;
+ }
+ if(w < 1 || w > SZ_LONG)
+ fatal(Z, "align");
+ if(packflg)
w = packflg;
break;
@@ -641,8 +649,8 @@
case Aarg0: /* initial passbyptr argument in arg list */
if(typesuv[t->etype]) {
- o = align(o, types[TIND], Aarg1);
- o = align(o, types[TIND], Aarg2);
+ o = align(o, types[TIND], Aarg1, nil);
+ o = align(o, types[TIND], Aarg2, nil);
}
break;
@@ -661,12 +669,14 @@
break;
case Aaut3: /* total align of automatic */
- o = align(o, t, Ael2);
- o = align(o, t, Ael1);
+ o = align(o, t, Ael2, nil);
+ o = align(o, t, Ael1, nil);
w = SZ_LONG; /* because of a pun in cc/dcl.c:contig() */
break;
}
o = xround(o, w);
+ if(maxalign != nil && *maxalign < w)
+ *maxalign = w;
if(debug['A'])
print("align %s %d %T = %d\n", bnames[op], i, t, o);
return o;
diff --git a/src/cmd/5c/txt.c b/src/cmd/5c/txt.c
index 1ba8ae2..0f17cea 100644
--- a/src/cmd/5c/txt.c
+++ b/src/cmd/5c/txt.c
@@ -388,7 +388,7 @@
void
regsalloc(Node *n, Node *nn)
{
- cursafe = align(cursafe, nn->type, Aaut3);
+ cursafe = align(cursafe, nn->type, Aaut3, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
*n = *nodsafe;
n->xoffset = -(stkoff + cursafe);
@@ -402,22 +402,22 @@
{
nodreg(n, nn, REGARG);
reg[REGARG]++;
- curarg = align(curarg, nn->type, Aarg1);
- curarg = align(curarg, nn->type, Aarg2);
+ curarg = align(curarg, nn->type, Aarg1, nil);
+ curarg = align(curarg, nn->type, Aarg2, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
}
void
regaalloc(Node *n, Node *nn)
{
- curarg = align(curarg, nn->type, Aarg1);
+ curarg = align(curarg, nn->type, Aarg1, nil);
*n = *nn;
n->op = OINDREG;
n->reg = REGSP;
n->xoffset = curarg + SZ_LONG;
n->complex = 0;
n->addable = 20;
- curarg = align(curarg, nn->type, Aarg2);
+ curarg = align(curarg, nn->type, Aarg2, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
}
diff --git a/src/cmd/6c/cgen.c b/src/cmd/6c/cgen.c
index dd8573c..9039488 100644
--- a/src/cmd/6c/cgen.c
+++ b/src/cmd/6c/cgen.c
@@ -1928,7 +1928,7 @@
int32
hi64v(Node *n)
{
- if(align(0, types[TCHAR], Aarg1)) /* isbigendian */
+ if(align(0, types[TCHAR], Aarg1, nil)) /* isbigendian */
return (int32)(n->vconst) & ~0L;
else
return (int32)((uvlong)n->vconst>>32) & ~0L;
@@ -1937,7 +1937,7 @@
int32
lo64v(Node *n)
{
- if(align(0, types[TCHAR], Aarg1)) /* isbigendian */
+ if(align(0, types[TCHAR], Aarg1, nil)) /* isbigendian */
return (int32)((uvlong)n->vconst>>32) & ~0L;
else
return (int32)(n->vconst) & ~0L;
diff --git a/src/cmd/6c/swt.c b/src/cmd/6c/swt.c
index 1597fdf..47975a0 100644
--- a/src/cmd/6c/swt.c
+++ b/src/cmd/6c/swt.c
@@ -503,7 +503,7 @@
}
int32
-align(int32 i, Type *t, int op)
+align(int32 i, Type *t, int op, int32 *maxalign)
{
int32 o;
Type *v;
@@ -517,7 +517,9 @@
break;
case Asu2: /* padding at end of a struct */
- w = SZ_VLONG;
+ w = *maxalign;
+ if(w < 1)
+ w = 1;
if(packflg)
w = packflg;
break;
@@ -525,10 +527,13 @@
case Ael1: /* initial align of struct element */
for(v=t; v->etype==TARRAY; v=v->link)
;
- w = ewidth[v->etype];
- if(w <= 0 || w >= SZ_VLONG)
- w = SZ_VLONG;
- if(packflg)
+ if(v->etype == TSTRUCT || v->etype == TUNION)
+ w = v->align;
+ else
+ w = ewidth[v->etype];
+ if(w < 1 || w > SZ_VLONG)
+ fatal(Z, "align");
+ if(packflg)
w = packflg;
break;
@@ -538,8 +543,8 @@
case Aarg0: /* initial passbyptr argument in arg list */
if(typesu[t->etype]) {
- o = align(o, types[TIND], Aarg1);
- o = align(o, types[TIND], Aarg2);
+ o = align(o, types[TIND], Aarg1, nil);
+ o = align(o, types[TIND], Aarg2, nil);
}
break;
@@ -560,11 +565,13 @@
break;
case Aaut3: /* total align of automatic */
- o = align(o, t, Ael1);
- o = align(o, t, Ael2);
+ o = align(o, t, Ael1, nil);
+ o = align(o, t, Ael2, nil);
break;
}
o = xround(o, w);
+ if(maxalign && *maxalign < w)
+ *maxalign = w;
if(debug['A'])
print("align %s %d %T = %d\n", bnames[op], i, t, o);
return o;
diff --git a/src/cmd/6c/txt.c b/src/cmd/6c/txt.c
index 29b2e13..a78ba22 100644
--- a/src/cmd/6c/txt.c
+++ b/src/cmd/6c/txt.c
@@ -424,7 +424,7 @@
void
regsalloc(Node *n, Node *nn)
{
- cursafe = align(cursafe, nn->type, Aaut3);
+ cursafe = align(cursafe, nn->type, Aaut3, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
*n = *nodsafe;
n->xoffset = -(stkoff + cursafe);
@@ -440,22 +440,22 @@
diag(n, "regaalloc1 and REGARG<0");
nodreg(n, nn, REGARG);
reg[REGARG]++;
- curarg = align(curarg, nn->type, Aarg1);
- curarg = align(curarg, nn->type, Aarg2);
+ curarg = align(curarg, nn->type, Aarg1, nil);
+ curarg = align(curarg, nn->type, Aarg2, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
}
void
regaalloc(Node *n, Node *nn)
{
- curarg = align(curarg, nn->type, Aarg1);
+ curarg = align(curarg, nn->type, Aarg1, nil);
*n = *nn;
n->op = OINDREG;
n->reg = REGSP;
n->xoffset = curarg;
n->complex = 0;
n->addable = 20;
- curarg = align(curarg, nn->type, Aarg2);
+ curarg = align(curarg, nn->type, Aarg2, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
}
diff --git a/src/cmd/8c/cgen64.c b/src/cmd/8c/cgen64.c
index ce1512c..3424f76 100644
--- a/src/cmd/8c/cgen64.c
+++ b/src/cmd/8c/cgen64.c
@@ -57,7 +57,7 @@
int32
hi64v(Node *n)
{
- if(align(0, types[TCHAR], Aarg1)) /* isbigendian */
+ if(align(0, types[TCHAR], Aarg1, nil)) /* isbigendian */
return (int32)(n->vconst) & ~0L;
else
return (int32)((uvlong)n->vconst>>32) & ~0L;
@@ -66,7 +66,7 @@
int32
lo64v(Node *n)
{
- if(align(0, types[TCHAR], Aarg1)) /* isbigendian */
+ if(align(0, types[TCHAR], Aarg1, nil)) /* isbigendian */
return (int32)((uvlong)n->vconst>>32) & ~0L;
else
return (int32)(n->vconst) & ~0L;
diff --git a/src/cmd/8c/swt.c b/src/cmd/8c/swt.c
index 46a0290..be48885 100644
--- a/src/cmd/8c/swt.c
+++ b/src/cmd/8c/swt.c
@@ -501,7 +501,7 @@
}
int32
-align(int32 i, Type *t, int op)
+align(int32 i, Type *t, int op, int32 *maxalign)
{
int32 o;
Type *v;
@@ -515,7 +515,9 @@
break;
case Asu2: /* padding at end of a struct */
- w = SZ_LONG;
+ w = *maxalign;
+ if(w < 1)
+ w = 1;
if(packflg)
w = packflg;
break;
@@ -523,10 +525,16 @@
case Ael1: /* initial align of struct element */
for(v=t; v->etype==TARRAY; v=v->link)
;
- w = ewidth[v->etype];
- if(w <= 0 || w >= SZ_LONG)
- w = SZ_LONG;
- if(packflg)
+ if(v->etype == TSTRUCT || v->etype == TUNION)
+ w = v->align;
+ else {
+ w = ewidth[v->etype];
+ if(w == 8)
+ w = 4;
+ }
+ if(w < 1 || w > SZ_LONG)
+ fatal(Z, "align");
+ if(packflg)
w = packflg;
break;
@@ -536,8 +544,8 @@
case Aarg0: /* initial passbyptr argument in arg list */
if(typesuv[t->etype]) {
- o = align(o, types[TIND], Aarg1);
- o = align(o, types[TIND], Aarg2);
+ o = align(o, types[TIND], Aarg1, nil);
+ o = align(o, types[TIND], Aarg2, nil);
}
break;
@@ -558,11 +566,13 @@
break;
case Aaut3: /* total align of automatic */
- o = align(o, t, Ael1);
- o = align(o, t, Ael2);
+ o = align(o, t, Ael1, nil);
+ o = align(o, t, Ael2, nil);
break;
}
o = xround(o, w);
+ if(maxalign && *maxalign < w)
+ *maxalign = w;
if(debug['A'])
print("align %s %d %T = %d\n", bnames[op], i, t, o);
return o;
diff --git a/src/cmd/8c/txt.c b/src/cmd/8c/txt.c
index 4cfd7bc..0dd387d 100644
--- a/src/cmd/8c/txt.c
+++ b/src/cmd/8c/txt.c
@@ -385,7 +385,7 @@
void
regsalloc(Node *n, Node *nn)
{
- cursafe = align(cursafe, nn->type, Aaut3);
+ cursafe = align(cursafe, nn->type, Aaut3, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
*n = *nodsafe;
n->xoffset = -(stkoff + cursafe);
@@ -399,22 +399,22 @@
{
nodreg(n, nn, REGARG);
reg[REGARG]++;
- curarg = align(curarg, nn->type, Aarg1);
- curarg = align(curarg, nn->type, Aarg2);
+ curarg = align(curarg, nn->type, Aarg1, nil);
+ curarg = align(curarg, nn->type, Aarg2, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
}
void
regaalloc(Node *n, Node *nn)
{
- curarg = align(curarg, nn->type, Aarg1);
+ curarg = align(curarg, nn->type, Aarg1, nil);
*n = *nn;
n->op = OINDREG;
n->reg = REGSP;
n->xoffset = curarg;
n->complex = 0;
n->addable = 20;
- curarg = align(curarg, nn->type, Aarg2);
+ curarg = align(curarg, nn->type, Aarg2, nil);
maxargsafe = maxround(maxargsafe, cursafe+curarg);
}
diff --git a/src/cmd/cc/cc.h b/src/cmd/cc/cc.h
index 69adccc..3649bf5 100644
--- a/src/cmd/cc/cc.h
+++ b/src/cmd/cc/cc.h
@@ -166,6 +166,7 @@
uchar nbits;
uchar etype;
uchar garb;
+ uchar align;
};
#define T ((Type*)0)
@@ -785,7 +786,7 @@
void sextern(Sym*, Node*, int32, int32);
void xcom(Node*);
int32 exreg(Type*);
-int32 align(int32, Type*, int);
+int32 align(int32, Type*, int, int32*);
int32 maxround(int32, int32);
extern schar ewidth[];
diff --git a/src/cmd/cc/dcl.c b/src/cmd/cc/dcl.c
index 3aaa2c1..f629925d 100644
--- a/src/cmd/cc/dcl.c
+++ b/src/cmd/cc/dcl.c
@@ -552,9 +552,10 @@
sualign(Type *t)
{
Type *l;
- int32 o, w;
+ int32 o, w, maxal;
o = 0;
+ maxal = 0;
switch(t->etype) {
case TSTRUCT:
@@ -577,13 +578,14 @@
l->sym->name);
else
diag(Z, "incomplete structure element");
- w = align(w, l, Ael1);
+ w = align(w, l, Ael1, &maxal);
l->offset = w;
- w = align(w, l, Ael2);
+ w = align(w, l, Ael2, &maxal);
}
}
- w = align(w, t, Asu2);
+ w = align(w, t, Asu2, &maxal);
t->width = w;
+ t->align = maxal;
acidtype(t);
pickletype(t);
return;
@@ -600,12 +602,13 @@
diag(Z, "incomplete union element");
l->offset = 0;
l->shift = 0;
- o = align(align(0, l, Ael1), l, Ael2);
+ o = align(align(0, l, Ael1, &maxal), l, Ael2, &maxal);
if(o > w)
w = o;
}
- w = align(w, t, Asu2);
+ w = align(w, t, Asu2, &maxal);
t->width = w;
+ t->align = maxal;
acidtype(t);
pickletype(t);
return;
@@ -663,7 +666,7 @@
{
Type *t;
- autoffset = align(0, thisfn->link, Aarg0);
+ autoffset = align(0, thisfn->link, Aarg0, nil);
stkoff = 0;
for(; n->left != Z; n = n->left) {
if(n->op != OFUNC || n->left->op != ONAME)
@@ -745,9 +748,9 @@
firstarg = s;
firstargtype = s->type;
}
- autoffset = align(autoffset, s->type, Aarg1);
+ autoffset = align(autoffset, s->type, Aarg1, nil);
s->offset = autoffset;
- autoffset = align(autoffset, s->type, Aarg2);
+ autoffset = align(autoffset, s->type, Aarg2, nil);
} else
dodecl(pdecl, CXXX, types[TINT], n);
break;
@@ -1275,7 +1278,7 @@
}
switch(c) {
case CAUTO:
- autoffset = align(autoffset, t, Aaut3);
+ autoffset = align(autoffset, t, Aaut3, nil);
stkoff = maxround(stkoff, autoffset);
s->offset = -autoffset;
break;
@@ -1285,10 +1288,10 @@
firstarg = s;
firstargtype = t;
}
- autoffset = align(autoffset, t, Aarg1);
+ autoffset = align(autoffset, t, Aarg1, nil);
if(s)
s->offset = autoffset;
- autoffset = align(autoffset, t, Aarg2);
+ autoffset = align(autoffset, t, Aarg2, nil);
break;
}
}
@@ -1587,7 +1590,7 @@
if(v != 0)
diag(n, "automatic adjustable array: %s", s->name);
v = s->offset;
- autoffset = align(autoffset, s->type, Aaut3);
+ autoffset = align(autoffset, s->type, Aaut3, nil);
s->offset = -autoffset;
stkoff = maxround(stkoff, autoffset);
symadjust(s, n, v - s->offset);
diff --git a/src/cmd/cc/pgen.c b/src/cmd/cc/pgen.c
index cd6fffc..a9d7f1e 100644
--- a/src/cmd/cc/pgen.c
+++ b/src/cmd/cc/pgen.c
@@ -37,7 +37,7 @@
int32 s;
//print("t=%T\n", thisfn);
- s = align(0, thisfn->link, Aarg0);
+ s = align(0, thisfn->link, Aarg0, nil);
for(t=thisfn->down; t!=T; t=t->down) {
switch(t->etype) {
case TVOID:
@@ -47,8 +47,8 @@
s += 64;
break;
default:
- s = align(s, t, Aarg1);
- s = align(s, t, Aarg2);
+ s = align(s, t, Aarg1, nil);
+ s = align(s, t, Aarg2, nil);
break;
}
//print(" %d %T\n", s, t);
@@ -99,7 +99,7 @@
nod1 = *nodret->left;
nod1.sym = firstarg;
nod1.type = firstargtype;
- nod1.xoffset = align(0, firstargtype, Aarg1);
+ nod1.xoffset = align(0, firstargtype, Aarg1, nil);
nod1.etype = firstargtype->etype;
nodreg(&nod, &nod1, REGARG);
gmove(&nod, &nod1);
diff --git a/src/cmd/cc/pswt.c b/src/cmd/cc/pswt.c
index 891836c..0e402de 100644
--- a/src/cmd/cc/pswt.c
+++ b/src/cmd/cc/pswt.c
@@ -115,7 +115,7 @@
r = nstring;
while(n > 0) {
c = *s++;
- if(align(0, types[TCHAR], Aarg1)) {
+ if(align(0, types[TCHAR], Aarg1, nil)) {
buf[0] = c>>8;
buf[1] = c;
} else {
diff --git a/src/cmd/gc/align.c b/src/cmd/gc/align.c
index 4b6d92e..a3785e8 100644
--- a/src/cmd/gc/align.c
+++ b/src/cmd/gc/align.c
@@ -49,8 +49,8 @@
if(f->etype != TFIELD)
fatal("widstruct: not TFIELD: %lT", f);
dowidth(f->type);
- if(f->align > maxalign)
- maxalign = f->align;
+ if(f->type->align > maxalign)
+ maxalign = f->type->align;
if(f->type->width < 0)
fatal("invalid width %lld", f->type->width);
w = f->type->width;
@@ -248,9 +248,11 @@
case TSTRUCT:
if(t->funarg)
fatal("dowidth fn struct %T", t);
- w = widstruct(t, 0, widthptr);
+ w = widstruct(t, 0, 1);
if(w == 0)
w = 1;
+ //if(t->align < widthptr)
+ // warn("align %d: %T\n", t->align, t);
break;
case TFUNC:
@@ -272,6 +274,8 @@
w = widstruct(*getinarg(t1), w, widthptr);
w = widstruct(*getoutarg(t1), w, widthptr);
t1->argwid = w;
+ if(w%widthptr)
+ warn("bad type %T %d\n", t1, w);
t->align = 1;
break;
}
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 5450862..4dd0d70 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -1124,7 +1124,7 @@
case OPRINT:
case OPRINTN:
ok |= Etop;
- typechecklist(n->list, Erv);
+ typechecklist(n->list, Erv | Eindir); // Eindir: address does not escape
goto ret;
case OPANIC:
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index a80112d..8b2c1a9 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -730,8 +730,6 @@
// Call calls the function fv with input parameters in.
// It returns the function's output parameters as Values.
func (fv *FuncValue) Call(in []Value) []Value {
- var structAlign = Typeof((*tiny)(nil)).(*PtrType).Elem().Size()
-
t := fv.Type().(*FuncType)
nin := len(in)
if fv.first != nil && !fv.isInterface {
@@ -757,7 +755,7 @@
size = (size + a - 1) &^ (a - 1)
size += tv.Size()
}
- size = (size + structAlign - 1) &^ (structAlign - 1)
+ size = (size + ptrSize - 1) &^ (ptrSize - 1)
for i := 0; i < nout; i++ {
tv := t.Out(i)
a := uintptr(tv.Align())
@@ -767,9 +765,9 @@
// size must be > 0 in order for &args[0] to be valid.
// the argument copying is going to round it up to
- // a multiple of 8 anyway, so make it 8 to begin with.
- if size < 8 {
- size = 8
+ // a multiple of ptrSize anyway, so make it ptrSize to begin with.
+ if size < ptrSize {
+ size = ptrSize
}
// round to pointer size
@@ -811,7 +809,7 @@
memmove(addr(ptr+off), v.getAddr(), n)
off += n
}
- off = (off + structAlign - 1) &^ (structAlign - 1)
+ off = (off + ptrSize - 1) &^ (ptrSize - 1)
// Call
call(*(**byte)(fv.addr), (*byte)(addr(ptr)), uint32(size))
diff --git a/src/pkg/runtime/debug.go b/src/pkg/runtime/debug.go
index 3cc5472..3ce35cc 100644
--- a/src/pkg/runtime/debug.go
+++ b/src/pkg/runtime/debug.go
@@ -4,6 +4,8 @@
package runtime
+import "unsafe"
+
// Breakpoint() executes a breakpoint trap.
func Breakpoint()
@@ -73,6 +75,15 @@
}
}
+var sizeof_C_MStats int // filled in by malloc.goc
+
+func init() {
+ if sizeof_C_MStats != unsafe.Sizeof(MemStats) {
+ println(sizeof_C_MStats, unsafe.Sizeof(MemStats))
+ panic("MStats vs MemStatsType size mismatch")
+ }
+}
+
// MemStats holds statistics about the memory system.
// The statistics are only approximate, as they are not interlocked on update.
var MemStats MemStatsType
diff --git a/src/pkg/runtime/hashmap.h b/src/pkg/runtime/hashmap.h
index 40dac6e..0737535 100644
--- a/src/pkg/runtime/hashmap.h
+++ b/src/pkg/runtime/hashmap.h
@@ -64,7 +64,6 @@
*/
#define malloc runtime·mal
-#define offsetof(s,m) (uint32)(&(((s*)0)->m))
#define memset(a,b,c) runtime·memclr((byte*)(a), (uint32)(c))
#define memcpy(a,b,c) runtime·mcpy((byte*)(a),(byte*)(b),(uint32)(c))
#define assert(a) if(!(a)) runtime·throw("assert")
diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc
index 405b05e..f5ca9f9 100644
--- a/src/pkg/runtime/malloc.goc
+++ b/src/pkg/runtime/malloc.goc
@@ -244,6 +244,8 @@
return c;
}
+int32 runtime·sizeof_C_MStats = sizeof(MStats);
+
void
runtime·mallocinit(void)
{
diff --git a/src/pkg/runtime/runtime.c b/src/pkg/runtime/runtime.c
index f2b6c58..a2e31d8 100644
--- a/src/pkg/runtime/runtime.c
+++ b/src/pkg/runtime/runtime.c
@@ -258,6 +258,13 @@
float64 j;
void* k;
uint16* l;
+ struct x1 {
+ byte x;
+ };
+ struct y1 {
+ struct x1 x1;
+ byte y;
+ };
if(sizeof(a) != 1) runtime·throw("bad a");
if(sizeof(b) != 1) runtime·throw("bad b");
@@ -271,7 +278,9 @@
if(sizeof(j) != 8) runtime·throw("bad j");
if(sizeof(k) != sizeof(uintptr)) runtime·throw("bad k");
if(sizeof(l) != sizeof(uintptr)) runtime·throw("bad l");
-// prints(1"check ok\n");
+ if(sizeof(struct x1) != 1) runtime·throw("bad sizeof x1");
+ if(offsetof(struct y1, y) != 1) runtime·throw("bad offsetof y1.y");
+ if(sizeof(struct y1) != 2) runtime·throw("bad sizeof y1");
uint32 z;
z = 1;
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index b0fa389..37c8103 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -306,6 +306,7 @@
*/
#define nelem(x) (sizeof(x)/sizeof((x)[0]))
#define nil ((void*)0)
+#define offsetof(s,m) (uint32)(&(((s*)0)->m))
/*
* known to compiler
